# ---
# title: 565. Array Nesting
# id: problem565
# author: Indigo
# date: 2021-06-26
# difficulty: Medium
# categories: Array
# link: <https://leetcode.com/problems/array-nesting/description/>
# hidden: true
# ---
# 
# A zero-indexed array A of length N contains all integers from 0 to N-1. Find
# and return the longest length of set S, where S[i] = {A[i], A[A[i]],
# A[A[A[i]]], ... } subjected to the rule below.
# 
# Suppose the first element in S starts with the selection of element A[i] of
# index = i, the next element in S should be A[A[i]], and then A[A[A[i]]]… By
# that analogy, we stop adding right before a duplicate element occurs in S.
# 
# 
# 
# **Example 1:**
# 
#     
#     
#     Input: A = [5,4,0,3,1,6,2]
#     Output: 4
#     Explanation: 
#     A[0] = 5, A[1] = 4, A[2] = 0, A[3] = 3, A[4] = 1, A[5] = 6, A[6] = 2.
#     
#     One of the longest S[K]:
#     S[0] = {A[0], A[5], A[6], A[2]} = {5, 6, 2, 0}
#     
# 
# 
# 
# **Note:**
# 
#   1. N is an integer within the range [1, 20,000].
#   2. The elements of A are all distinct.
#   3. Each element of A is an integer within the range [0, N-1].
# 
# 
## @lc code=start
using LeetCode

function array_nesting(nums::Vector{Int})
    visited = fill(false, length(nums))
    res = 0
    for (idx, num) in enumerate(nums)
        num += 1
        visited[idx] && continue
        tmp = 1
        visited[idx] = true
        while !visited[num]
            visited[num] = true
            num = nums[num] + 1
            tmp += 1
        end
        res = max(res, tmp)
    end
    return res
end
## @lc code=end
